Question

我想帮助添加一个UNION来获取查询的所有月份。我尝试在一堆斑点中添加联合但是却无法正确使用它。

SELECT MONTH(FirstPublishedToPortal) AS theMonth,
   YEAR(FirstPublishedToPortal) AS theYear,
   MONTHNAME(FirstPublishedToPortal) AS theMonthName,
   COUNT(DISTINCT PONum) AS POCount,

   SUM(unconfirmedEmailSent) AS unconfirmedEmailsSent,
   ( SELECT COUNT(DISTINCT PONum)
     FROM POFlags
     WHERE unconfirmedEmailSent = 0
     AND MONTH(FirstPublishedToPortal) = theMonth
     AND YEAR(FirstPublishedToPortal) = theYear
     AND VendorNum = '2222'
   ) AS onTimeConfirmed,

   SUM(lateEmailSent) AS lateEmailsSent,
   ( SELECT COUNT(DISTINCT PONum)
     FROM POFlags
     WHERE lateEmailSent = 0
     AND MONTH(FirstPublishedToPortal) = theMonth
     AND YEAR(FirstPublishedToPortal) = theYear
     AND VendorNum = '2222'
   ) AS onTimePOCount

FROM POFlags

WHERE VendorNum = '2222'
   AND FirstPublishedToPortal >= '2017-01-08'

GROUP BY theYear DESC, theMonth DESC
ORDER BY FirstPublishedToPortal DESC

此查询中的union子句在哪里？我认为需要有类似下面的代码，但我不明白在哪里使用GROUP BY或ORDER BY正常工作。

(SELECT 1, null, 'January', 0, 0, 0, 0, 0)
UNION 
(SELECT 2, null, 'February', 0, 0, 0, 0, 0)
UNION 
(SELECT 3, null, 'March', 0, 0, 0, 0, 0)
.    
.
(SELECT 12, null, 'December, 0, 0, 0, 0, 0)

SQL FIDDLE HERE

Answer 1

使用基于带联合的嵌套查询的左连接。

使用Coalesce应用默认值。

移动连接子句

的条件

警告，2017年是硬编码的

像这样：http://sqlfiddle.com/#!9/458808/27

SELECT
    all_month.nMonth AS theMonth, 
    coalesce(YEAR(FirstPublishedToPortal),2017) AS theYear,
    all_month.sMonth AS theMonthName,
    coalesce(COUNT(DISTINCT PONum),0) AS POCount,

    coalesce(SUM(unconfirmedEmailSent),0) AS unconfirmedEmailsSent,
    coalesce(( SELECT COUNT(DISTINCT PONum)
       FROM POFlags
       WHERE unconfirmedEmailSent = 0
         AND MONTH(FirstPublishedToPortal) = theMonth
         AND YEAR(FirstPublishedToPortal) = theYear
         AND VendorNum = '2222'
    ),0) AS onTimeConfirmed,

    coalesce(SUM(lateEmailSent),0) AS lateEmailsSent,
    coalesce(( SELECT COUNT(DISTINCT PONum)
       FROM POFlags
       WHERE lateEmailSent = 0
         AND MONTH(FirstPublishedToPortal) = theMonth
         AND YEAR(FirstPublishedToPortal) = theYear
         AND VendorNum = '2222'
     ),0) AS onTimePOCount
FROM (
     (SELECT 1 nMonth, 'January' sMonth)   UNION ALL
     (SELECT 2 nMonth, 'February' sMonth ) UNION ALL
     (SELECT 3 nMonth, 'March' sMonth )    UNION ALL
     (SELECT 4 nMonth, 'April' sMonth )    UNION ALL
     (SELECT 5 nMonth, 'May' sMonth )      UNION ALL
     (SELECT 6 nMonth, 'June' sMonth )     UNION ALL
     (SELECT 7 nMonth, 'July' sMonth )     UNION ALL
     (SELECT 8 nMonth, 'August' sMonth )   UNION ALL
     (SELECT 9 nMonth, 'September' sMonth) UNION ALL
     (SELECT 10 nMonth, 'October' sMonth ) UNION ALL
     (SELECT 11 nMonth, 'November' sMonth )UNION ALL    
     (SELECT 12 nMonth, 'December' sMonth)
     ) all_month left join POFlags on
         MONTH(FirstPublishedToPortal)=nMonth and
         VendorNum = '2222' and
         FirstPublishedToPortal >= '2017-01-08'
GROUP BY
    theYear DESC, nMonth DESC
ORDER BY
    nMonth DESC

使用原始结果和默认值之间的全局联合存在另一种方法，但此方法需要第二组...

将UNION添加到MySQL中的复杂SELECT中

1 个答案: